ASP.NET:
<telerik:RadToggleButton ID="btnFormFactor" runat="server" RenderMode="Lightweight">
<ToggleStates>
<telerik:ButtonToggleState Value="1" Text="Force screen size Small"></telerik:ButtonToggleState>
<telerik:ButtonToggleState Value="3" Text="Force screen size Normal"></telerik:ButtonToggleState>
</ToggleStates>
</telerik:RadToggleButton>
Code Behind:
Private Sub btnFormFactor_Click(sender As Object, e As EventArgs) Handles btnFormFactor.Click
'we're storing the state in the session to preserve it between page calls
'note that the ToggleStates array is 0 based
If Session("ForceScreenSize") = 3 Then
Me.btnFormFactor.ToggleStates(0).Selected = True
Session("ForceScreenSize") = 1
Else
Me.btnFormFactor.ToggleStates(1).Selected = True
Session("ForceScreenSize") = 3
End If
End Sub